Dexiu Huang’s research while affiliated with Huazhong University of Science and Technology and other places

A novel scheme is proposed for frequency 24-tupling millimeter-wave generation based on two cascaded integrated dual-parallel Mach-Zehnder modulators (MZM) without optical filtering. Simulation verifications are provided for the microwave frequency multiplication scheme. Optical sideband suppression ratio (OSSR) higher than 33 dB and radio frequency spurious sideband suppression ratio (RSSR) higher than 26 dB are achieved without optical filters. In addition, a 2.5 Gbit/s data distribution performances are also evaluated for both dual tone and single tone modulation formats.

Silicon micro-ring resonators (MRRs) are compact and versatile devices whose periodic frequency response can be exploited for a wide range of applications. In this paper, we review our recent work on linear all-optical signal processing applications using silicon MRRs as passive filters. We focus on applications such as modulation format conversion, differential phase-shift keying (DPSK) demodulation, modulation speed enhancement of directly modulated lasers (DMLs), and monocycle pulse generation. The possibility to implement polarization diversity circuits, which reduce the polarization dependence of standard silicon MRRs, is illustrated on the particular example of DPSK demodulation. © 2016, Higher Education Press and Springer-Verlag Berlin Heidelberg.

A comprehensive analysis of photonically assisted microwave frequency multiplication based on two cascaded Mach-Zehnder modulators (MZMs) is presented. The expressions, including all harmonics, are entirely general in terms of the extinction ratio (EXT) of MZM. A theoretical derivation that induces operating conditions is developed to achieve frequency quadrupling, sextupling, and octupling. The impact of an imperfect EXT of MZM on optical sideband suppression ratio and RF spurious suppression ratio is investigated. The improvement of system performance through MZM modulation index optimization is also analyzed. Simulation verifications are provided for the microwave frequency multiplication schemes.

A novel scheme is proposed for frequency 12-tupling millimeter-wave generation based on two cascaded dual-parallel Mach–Zehnder modulators (DP-MZM) without optical filtering. The impact of imperfect extinction ratio (EXT) of each sub-MZM on optical sideband suppression ratio (OSSR) and RF spurious suppression ratio (RSSR) is investigated. Theoretical and simulation results show that the proposed scheme is feasible and system performance is insensitive to EXT when EXT is not less than 29 dB. Optical mm-wave with 26.4 dB OSSR and 20.3 dB RSSR can be obtained when the DPMZM is consisted of two sub-MZMs with 30 dB EXT. Furthermore, the system performance improvement through sub-MZM modulation index enhancement is analyzed.

The transmission performance of single sideband (SSB) radio over fiber (RoF) system is evaluated through tuning the modulation index of Mach-Zehnder modulator, two different data modulation schemes and the influence of fiber dispersion are considered. The quantitative simulation results validate that there exist an optimum modulation index, and the system performance could be improved if the data signal is modulated on only optical carrier or sidebands.

Ultra-wide band signal generation using a silicon microring resonator tuned to an NRZ-DPSK modulated optical carrier is proposed and demonstrated. The scheme is shown to enable the generation of UWB signals with switchable polarity and tunable bandwidth by simply tuning the coupling regions of the microring resonator. Monocycle pulses with both negative and positive polarities are successfully synthesized experimentally.

As a tunable optical filter, angle-tuned thin film narrowband filter is widely used in dense wavelength division multiplexing (DWDM) system. In oblique incidence, the transmitting facular broadens obviously, which will cause a decrease in transmissivity and rectangular degree of the filter. The transmitting spectrum characteristics and the transmitting facular broadening are also influenced by the non-parallel incident and emergent interfaces' wedge angle of the wedge filter. In the present paper, the transmitting intensity distribution in different incident angle of the wedge filter has been calculated, and the influences of the wedge angle to the transmissivity and the half bandwidth are also analyzed. The proper wedge angle and incident orientation will improve the characteristics of the transmitting spectrum. A 100 GHz DWDM angle-tuned wedge filter was fabricated which has a wedge angle of 0.8°. Compared with the parallel angle-tuned filter, the wedge filter can enhance the transmissivity and the rectangular degree in oblique incidence and its tunable wavelength range will increase 10 nm.

We put forward a hybrid coding method of multiple orbital angular momentum (OAM) states based on the inherent orthogonality. Theoretical analysis shows this new coding method can tremendously improve the coding efficiency compared to the conventional way, and the OAM mode can be extended to all the transverse orthographic modes such as Bessel beams or Laguerre–Gauss modes. We also present a typical scheme to achieve the encoding of hybrid OAM states based on a concentric ring resonator array. We further suggest a digital device and a phase hologram pattern to decode the hybrid OAM states.

Angle-tuned thin film bandpass filter is widely used in DWDM system. In oblique incidence, the bandwidths and central wavelengths of the P-polarization and S-polarization light will separate obviously, which will cause serious polarization dependent loss. These phenomena of the polarization sensitivities are analyzed and a novel non-polarization 100 GHz four-cavity narrowband dielectric thin film stack used in oblique incidence is proposed. The simulation results show that it can eliminate the polarization bandwidths and central wavelengths separation within the incident angle from 0 to 25 and its tunable range can cover the whole C-band.